Vulcanization of rubber



Patented Nov. 16, 1943 UNITE. STATES 1 "rain c: J hesa nd Roger A. 031m {NoprawingN ApplicatiornE'eliiuany Seria LNo. 55.35%":

6 Claims; (Cl. 260L782) 1 HzCN are poor. accelerators. of. vulcanization.

We haye'disclosed in; our copending application Seria-lNo. 255,358} filed February 8, 1939, that Z-mercaptothiazolines are good accelerators when employed in the presence of carboxylic acids and their metallic salts.

We have now discovered that guanidine salts of 2-mercaptothiazolines are excellent accelerators of vulcanization, even in the absence of any carboxylic acid. Mono-, di-, triortetrasubstituted thiazolines as well as mono-, di-, tri-, tetra-, and penta-substituted guanidines containing such substituents as methyl, ethyl, isopropyl, isopropenyl, benzyl, cyclohexyl, phenyl, naphthyl, xenyl, tolyl (ortho, meta, or para), indyl, anthryl, phenanthryl, or other hydrocarbon groups as well as compounds containing allphatic or aromatic groups with non-acid substituents such as alkoxy-alkyl, alkoxy-aryl, nitroaryl, arxyloxy-aryl; chlor-alkyl, chlor-aryl, arylamino-aryl, dialkylamino-aryl, and arylamidoaryl groups may be employed to form the accelerators of this invention. The preferred compounds are the salts of Z-mercaptothiazolines with diaryl guanidines such as diphenyl guanidine.

The guanidine salts of the 2-mercaptothiazolines may be prepared by the methods well known to the art. Thus when solutions of equimolar amounts of Z-mercaptothiazoline and diphenyl guanidine in hot alcohol are combined and allowed to cool, the diphenyl guanidine salt of 2- mercaptothiazoline precipitates. Other methods of preparation such as the reaction between a metallic salt of a 2-mercaptothiazoline and a guanidine hydrochloride may be employed.

As an illustration of the accelerating power of theguanidine .S tSQ 2- r p mmam1m Sulfur Diphenyl guanidine salt of 2-mercaptoth1azoline Laurie a id I j Whmthesg p inq i tib swe he'atedmo'ldfor varylng'time -i. c mpositions having the following"tensile'sti'engtlis in pounds per square inch and elongations in per cent were obtained-z Composition Time of we iiimihutes" A B" T E T E 3::: 31333 333'i1% it? It will be observed that although the lauric acid had a slight activating effect, the diphenyl guanidine salt of 2-mercaptothiazoline was itself an excellent accelerator. Similar results may be obtained by employing as accelerators other guanidine salts of 2-mercaptothiazolines as disclosed above.

It is not essential to the successful practice of our invention that the salts be prepared prior to the incorporation in the rubber composition. Thus, if Z-mercaptothiazoline and diphenyl guanidine are incorporated in a rubber composition, the salt will be formed in situ during vulcanization and the rate of cure of the composition will approximate that which would have been obtained had the .salt been prepared before. incorporation m the rubber. I

Although the use of the accelerators of this invention has been described in detail in connection with specific rubber compositions, it will be evident that this invention is applicable to rubber compositions of the most varied nature, and that all manner of rubber goods including pneumatic and solid rubber tires, tubes, hose, belting, packing, boots and shoes, surgical rubber goods, seamless dipped rubber articles, etc., may be vulcanized in the presence of the accelerators herein described. The accelerator may be incor-v porated in the rubber masticatiommilling, or

any similar process, or in the case of latex, rub

ber cement, or any other natural or artificial dispersion or solution of rubber by simply mssolving or suspending the accelerator therein. The vulcanization may be performed in other manners than that particularly set forth in the specific examples; specifically/rubber composi-; tions may be heated in the presence of sulfur or selenium in hot air, steam, hot water, etc.

It is tobe understood that the term a rubber is employed in the appended claims in a generic sense to designate those rubbery materials which are vulcanizable with sulfursin cluding caoutchouc, balata, gutta percha, latexyrrubber isomers, or synthetic rubber whether or not admixed with pigments, fillers, softeners, antioxidants, other accelerators, etc., but not including mate-'- rials incapable of vulcanization by reaction with sulfur.

Whilewe have herein disclosed specific embodiments of our invention," we do not intend to limit ourselves solely thereto, for it will be occupied hydrocarbon groups are occupied by hydrogen.

2. The process which comprises vulcanizing a rubber in the presence of 2-mercaptothiazoline salt of a diaryl guanidine which has the structure J I in which two of the free valences are occupied by aryl groups and the other three by hydrogen.

3. The process which comprises vulcanizing a rubber in the presence of the diphenyl guanidine salt of 2-mercaptothiazollne.

4. A rubber which has been vulcanized in the obvious to those skilled in the art that many modifications such as using other materials having equivalent properties and varying the proportions 'of materials used arewitmn the spirit and scope of the invention as defined in the appended claims. Y ,We' claim: I

1. The process which rubber in the presence ofa 2-mercaptothiazoline comprises vulcanizing a salt of a hydrocarbon. substituted guanidine which in which those of the free valences which are not structure 1 V N l l in which'those of the free valences which are not occupied by hydrocarbon groups are occupied by hydrogen. a r i 5. A rubber which has been vulcanized in the presence of 2-mercaptothiazoline salt of a diaryl guanidine which has the structure No- N in which two of the free valences are occupied by aryl groups and the other three by hydrogen.

6. A rubber which has been vulcanized in the presence of the diphenyl guanidine salt of 2- mercaptothiazoline. p 7

PAUL C. JONES. ROGER A. MATHES.

CERTIFICATE OF CORRECTION. Patent NO 2, L 650; November 16, 1915.

PAUL c. JONES, ET AL.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 1, first column, line 58, for "arxyloxy-aryl read aryloxy-ary1; page 1, second column, in the first formula, last line thereof, for the figure "1" 'under "A", opposite "Laurie acid", read O; and that the said Letters Patent should be read with this correction therein that the same maj conform to the record of the case in the Patent Office.

Signed and sealed this 1st day of February, A. D. 19141 Henry Van Arsdale, (Seal) Acting Commissioner of Patents. 

